Temperature control apparatus and method with recirculated coolant

ABSTRACT

A temperature control and process for adjusting the temperature of a workstation and a work medium at a workstation to a predetermined temperature. The temperature control comprises a cooling vehicle such as a heat exchanger, a coolant temperature sensor and control, a source of fluid coolant such as a manifold, a recirculating pump, a flow line to circulate the coolant to the workstation with the flow line containing a flow regulator and a heater, a bypass valve for bypassing the flow regulator and heater, and a workstation temperature sensor and control. The workstation temperature control controls the operation of the heater and bypass valve so that the temperature of the coolant is below the desired temperature for the workstation, thus achieving a rapid transient response while avoiding overcooling. The coolant temperature control and workstation temperature control may be in a temperature control computer, thus providing a large number of different operating sequences. A number of embodiments of workstations are also described.

[0001] This application is a continuation of copending application Ser.No. 08/184,681 filed on Jan. 21, 1994.

[0002] This invention relates to a temperature control apparatus andmethod with recirculated coolant for rapidly cooling a workstation witha work medium or workpiece to a set temperature.

BACKGROUND OF THE INVENTION

[0003] Applications such as photoresist processing on semiconductorwafers require very precise temperature control of chemicals and siliconwafers. To achieve such precise control of temperatures, temperaturecontrols with recirculated coolant are used.

[0004] Most temperature controls of this type use a recirculatedcoolant, such as water, for temperature control at or around roomtemperature. Most such temperature controls require large flow rates inorder to achieve rapid transient response, since the coolant is set atthe temperature to be achieved in the material being controlled and heattransfer near the set point is very slow. Most such temperature controlsalso require multiple circulators to achieve temperature control ofmultiple workstations at different temperatures.

SUMMARY OF THE INVENTION

[0005] An object of the invention is to provide a temperature controlwith rapid transient response with minimal flow rates.

[0006] A second object of the invention is to provide a temperaturecontrol which uses only one circulator to achieve control of temperatureof multiple workstations.

[0007] A feature of the invention is the apparatus for producing coolingat a workstation sufficient to rapidly bring the workstation and a solidor fluid work medium therein to a predetermined temperature, i.e., forachieving a rapid transient response, i.e., the time required to coolthe workstation from its initial temperature to a temperature closelyapproaching that desired. Such rapid cooling is achieved by introducinginto the workstation a coolant at a lower temperature than thepredetermined temperature, and by adding heat to the coolant in its flowline as the temperature in the workstation nearly simulates the desiredpredetermined temperature.

[0008] Another feature of the invention is the apparatus for adjustingthe temperature of a workstation, thus providing the ability to set theworkstation temperature below, at, or above the ambient temperature.

[0009] Another feature of the invention is the apparatus for circulatingcoolant to multiple workstations with only one circulator. Having onlyone circulator for multiple workstations increases reliability andreduces cost versus multiple circulator approaches.

[0010] Another feature of the invention is the apparatus for adjustingthe temperature of multiple workstations. In this way, each workstationmay have a separate set point temperature below, at, or above itsambient temperature.

[0011] Still another feature of the invention is the method of providingcontrol of temperature to multiple workstations, wherein rapid transientresponse is achieved by momentarily introducing a flow of unwarmedcoolant to the workstations, wherein only one circulator is used, andwherein the coolant temperature is slightly below the temperature of theworkstations, the coolant being precisely warmed at each workstation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a diagrammatic sketch of the temperature controlapparatus.

[0013]FIG. 2 is a perspective view of one possible work station whosetemperature is being controlled.

[0014]FIG. 3 is a perspective view of a second possible work stationwhose temperature is being controlled.

[0015]FIG. 4 is a perspective view of a third possible work stationwhose temperature is being controlled.

[0016]FIG. 5 is a perspective view of a fourth possible work stationwhose temperature is being controlled.

[0017]FIG. 6 is a graph of one possible time sequence for controlling aworkstation's temperature.

[0018]FIG. 7 is a graph of a second possible time sequence forcontrolling a workstation's temperature.

DETAILED SPECIFICATION OF THE PREFERRED EMBODIMENTS

[0019] An embodiment of the invention is indicated in FIG. 1 by thenumeral 10. The invention comprises first a source of fluid coolant anda means for maintaining the fluid coolant at a temperature below apredetermined temperature at or around room temperature. The inventionmaintains the fluid coolant temperature within a tolerance of ±0.5° C.

[0020] The means for maintaining the fluid coolant below a predeterminedtemperature comprises a cooling vehicle and associated controls. Acooling vehicle 12, such as a heat exchanger, cools the fluid coolant toa temperature below that desired for the workstation and work medium orworkpiece. A main coolant temperature sensor 14 detects the temperatureof the fluid coolant. Upon detecting the temperature of the fluidcoolant, the temperature sensor 14 provides an indication of thistemperature to a main coolant temperature control 16 by means of asensor lead 18, such as a wire or other means of transmission. Actingupon set point information provided by the operator, the main coolanttemperature control 16 signals the cooling vehicle 12, by means of acontrol lead 20, which may be a wire or other transmission medium, toremove enough heat from the fluid coolant to establish and maintain thetemperature of the fluid coolant at the desired temperature, which isbelow that desired for the workstation and work medium or workpiece. Themain coolant temperature control 16 may be in a programmed temperaturecontrol computer 22.

[0021] Coolant from the cooling vehicle 12 enters a source of fluidcoolant, such as a pipe or manifold 24. In this embodiment of theinvention, the temperature sensor 14 described above is within orattached to the manifold 24, thus sensing the temperature of the fluidcoolant at the manifold 24.

[0022] Coolant from the cooling vehicle 12 and manifold 24 is circulatedto and through the workstation 28 by coolant circulating meanscomprising a flow line 26, return line 32 and a recirculating pump 30.

[0023] Fluid coolant 25 from the manifold 24 enters the flow line 26.The flow line 26 preferably contains a flow regulator 34 which maintainsthe desired rate of flow of liquid coolant through the flow line 26. Aspecific embodiment of such a flow regulator is a fixed orifice. Theflow line 26 also contains a heater 36 such as an electrical resistanceheater for regulating the temperature of the fluid coolant flowing tothe workstation 28, and continuously adding heat when called for, to thecontinuously flowing coolant fluid.

[0024] Fluid coolant enters the workstation 28 from the flow line 26,passes through the workstation 28, and exits the workstation 28 into theflow line 26. Coolant then returns to the recirculating pump 30 andcooling vehicle 12 by return line 32. Coolant from the manifold 24 alsodirectly returns to the recirculating pump 30 and cooling vehiclethrough return line 32.

[0025] As the fluid coolant passes through the workstation 28, the fluidcoolant adjusts the temperature of the workstation 28 to the temperatureof the fluid coolant by heat transfer. Although the coolant in the flowline 26 is normally cooler than the workstation 28, coolant in the flowline 26 may also be at a higher temperature than that of the workstation28. The workstation 28 is closely associated with a work medium orworkpiece 38 whose temperature is to be controlled, the temperature ofthe work medium or workpiece thus approximating that of the workstation.

[0026] The workstation 28 has associated with it a workstationtemperature sensor 40, in such a manner that the temperature sensor 40detects the temperature of the workstation 28. Upon detecting thetemperature of the workstation 28, the temperature sensor 40 provides anindication of this temperature to a control means, workstationtemperature control 42 by means of a sensor lead 44, such as a wire orother transmission medium. The set point temperature to be maintained atthe workstation 28 is provided to the workstation temperature control 42by the operator. The workstation temperature control 42 may be in aprogrammed temperature control computer, thus providing a great deal offlexibility and precision in regulating the temperature of theworkstation. The workstation temperature control 42 compares thetemperature indication from the workstation temperature sensor 40 to thedesired temperature, and takes appropriate action to adjust theworkstation temperature to the desired temperature.

[0027] To adjust the workstation temperature to the desired temperature,the workstation temperature control 42 signals the heater 36 to providemore or less heat by means of a control lead 46, which may be a wire orother transmission medium. The heater heats only that portion of thecoolant flowing in flow line 26 to the workstation 28, rather than theentire source of coolant. This provides for precise and rapid control ofthe temperature of the workstation.

[0028] The flow line also contains a means, such as a valve 48, forbypassing both the flow regulator 34 and the heater 36. When the bypassvalve 48 is opened, it will be seen that a flow of unwarmed coolant willbe supplied to the workstation 28 at an increased rate of flow, thusrapidly cooling the workstation 28. The valve 48 is controlled by theworkstation temperature control 42 by means of a control lead 50, whichmay be a wire or other transmission medium.

[0029] It will be appreciated by those skilled in the art that thesequence in which the bypass valve 48 and heater 36 are operated willdepend upon the rapidity of the transient response required, and theinitial temperature differential between the temperature of theworkstation 42 and the desired temperature. At one extreme, an initiallarge temperature differential such as 5° C. might cause the workstationtemperature control 42 to open the bypass valve 48 initially. At theother extreme, an initially small temperature differential such as 0.5to 1.0° C. might cause the temperature control 42 to keep the bypassvalve 48 closed. As the temperature control 42 may be embodied in atemperature control computer, a large number of different operatingsequences may be programmed into the computer, and the appropriatesequence selected for the particular situation presenting itself.

[0030] For example, FIG. 6 is a graph of workstation temperature versustime. The workstation is to be cooled from an initial temperature T₁,for example 22° C. to a desired temperature T₂ perhaps 20° C. somewhatabove the temperature of the fluid coolant T₃, such as 19° C. In thisexample the workstation temperature control 42 might initially close thebypass valve 48, and turn off the heater 36. When the workstationtemperature falls to a predetermined value T₄ the workstationtemperature control 42, as set by the operator, signals the heater 36 tobegin supplying heat to the flow line 26. The temperature of theworkstation 28 then decreases less rapidly as depicted by the graph lineL₁, until the temperature of the workstation 28 reaches the desiredtemperature T₂, as depicted at point P₁. The workstation temperaturecontrol 42 then precisely modulates the heater 36 in order to maintainthe temperature of the workstation 28 at the desired temperature T₂.

[0031]FIG. 7 shows a second example. Here the workstation, starts out ata higher temperature T₁, perhaps 25° C. The workstation temperaturecontrol 42 opens the bypass valve 48 providing rapid cooling of theworkstation 28 as depicted by the chart line L₁. As the workstationtemperature approaches desired temperature T₂, perhaps 20° C., somewhatabove the temperature of the fluid coolant T₃, such as 19° C., theworkstation temperature control 42 closes the bypass valve 48, thusshutting off the high-rate flow of unheated coolant. The workstationtemperature control 42 then precisely modulates the heater 36 tomaintain the temperature of the workstation 28 at temperature T₂.

[0032] A plurality of workstations 28, 28.1, 28.2 may be regulated bythe invention through flow lines 26, 26.1, 26.2, heaters 36, 36.1, 36.2,flow regulators 34, 34.1, 34.2, bypass valves 48, 48.1, 4.2, workstationtemperature sensors 40, 40.1, 40.2 and workstation temperature controls42, 42.1, 42.2. Having one temperature control regulate a number ofworkstations can result in cost savings. At the same time, replicatingthe workstation temperature and flow controls allows each workstation tobe independently controlled to an independent predetermined temperature,if so desired.

[0033] A first embodiment of a workstation is shown in FIG. 2, where theworkstation 28 comprises a chill plate through which the fluid coolantis circulated from the flow line 26. The chill plate has an uppersurface 29.1 upon which the workpiece 38 rests. In this embodiment theworkpiece may be a semiconductor wafer whose temperature is to becontrolled.

[0034] A second embodiment of a workstation is shown in FIG. 3, wherethe workstation 28 comprises a cylindrical collar with an interiorcylindrical passage 29.2 through which the work medium 38.1 extends. Inthis embodiment, the work medium 38.1 may be the shaft 39 of an electricmotor 52. The fluid coolant circulates from the flow line 26 in and outof the workstation 28. The workstation 28 thereby regulates thetemperature of the shaft 39, thus preventing heat from the motor 52 fromreaching the workpiece 54, which can be a wafer supported on a rotatingchuck 56 on the end of the shaft 39.

[0035] A third embodiment of a workstation is shown in FIG. 4, where theworkstation 28 comprises a liquid-to-liquid heat exchanger with aninterior pipe 29.3 through which a liquid work medium to be cooled 38.2is flowing. The fluid coolant circulates from the flow line 26 in andout of the workstation 28, thereby regulating the temperature of theliquid work medium 38.2.

[0036] A fourth embodiment of a workstation is shown in FIG. 5, wherethe workstation 28 comprises a module with an upper compartment 29.4 andlower compartment 29.5 separated by a cooling plate 29.6. The fluidcoolant circulates from the flow line 26 in and out of the cooling plate29.6, thereby preventing thermal interactions between processes in theupper compartment 29.4 and the lower compartment 29.5.

[0037] It will be seen that a temperature control with recirculatedcoolant and a rapid transient response has been described. A process forprecisely cooling a work medium to a predetermined temperature has alsobeen described.

[0038] The present invention may be embodied in other specific formswithout departing from the spirit or essential attributes thereof;therefore, the illustrated embodiment should be considered in allrespects as illustrative and not restrictive, reference being made tothe appended claims rather than to the foregoing description to indicatethe scope of the invention.

What is claimed:
 1. A temperature control for adjusting the temperatureof a workstation and a work medium at a workstation to a predeterminedtemperature, comprising: workstation temperature sensing means todetermine the temperature of the workstation, a source of fluid coolantand means for maintaining the fluid coolant at a temperature below saidpredetermined temperature, coolant circulating means comprising a flowline delivering coolant from said source and to and through theworkstation and adjusting the temperature of the workstation and workmedium therein, a coolant heater in the flow line heating the coolantbeing supplied to the workstation to a temperature nearly equal to saidpredetermined temperature as to maintain the workstation and work mediumat said predetermined temperature, and control means for the heater andmodulating the heating thereof, said control means reducing the heatingby said heater while a substantial differential exists between theworkstation temperature and said predetermined temperature, and saidcontrol means increasing the heating by said heater as said differentialdecreases and as the workstation temperature nearly achieves saidpredetermined temperature.
 2. A temperature control as in claim 1 ,further comprising means for regulating the flow of coolant in the flowline.
 3. A temperature control as in claim 2 , further comprising meansfor bypassing said flow regulating means and said heater, and whereinsaid control means controls said bypass means.
 4. A temperature controlas in claim 3 , wherein said control means is a temperature controlcomputer, and the computer's program controls said heater and saidbypass means.
 5. A temperature control as in claim 1 , wherein saidtemperature control controls the temperature of a plurality ofworkstations and work media therein.
 6. A temperature control foradjusting the temperature of a workstation and a work medium at aworkstation to a predetermined temperature, comprising: a workstation,workstation temperature sensing means to determine the temperature ofthe workstation, a source of fluid coolant and means for maintaining thefluid coolant at a temperature below said predetermined temperature,coolant circulating means comprising a flow line delivering coolant fromsaid source and to and through the workstation and producing cooling ofthe workstation and work medium therein, a coolant heater in the flowline heating the coolant being supplied to the workstation to atemperature nearly equal to said predetermined temperature as tomaintain the workstation and work medium at said predeterminedtemperature, and control means for the heater and modulating the heatingthereof, said control means reducing the heating by said heater while asubstantial differential exists between the workstation temperature andsaid predetermined temperature, and said control means increasing theheating by said heater as said differential decreases and as theworkstation temperature nearly achieves said predetermined temperature.7. A temperature control as in claim 6 , further comprising means forregulating the flow of coolant in the flow line.
 8. A temperaturecontrol as in claim 7 , further comprising means for bypassing said flowregulating means and said heater, and wherein said control meanscontrols said bypass means.
 9. A temperature control as in claim 8 ,wherein said control means is a temperature control computer, and thecomputer's program controls said heater and said bypass means.
 10. Atemperature control as in claim 6 , wherein said workstation comprises acooling plate for supporting a wafer whose temperature is to beregulated.
 11. A temperature control as in claim 6 , wherein saidworkstation comprises a cylindrical collar encompassing a shaft to becooled, said shaft being connected to an electric motor at one end, andsaid shaft having a chuck at the end of said shaft distal from saidmotor, said chuck supporting a wafer whose temperature is to beregulated.
 12. A temperature control as in claim 6 , wherein saidworkstation comprises a liquid-to-liquid heat exchanger for regulatingthe temperature of a fluid passing through said heat exchanger.
 13. Atemperature control as in claim 6 , wherein said workstation comprises amodule having an upper compartment, a lower compartment, and a coolingplate separating said upper compartment from said lower compartment,said module regulating the temperature of materials in said uppercompartment and said lower compartment.
 14. A temperature control as inclaim 6 , wherein said temperature control controls the temperature of aplurality of workstations and work media therein.
 15. A temperaturecontrol for adjusting the temperature of a workstation and a work mediumat a workstation to a predetermined temperature, comprising: a source offluid coolant, a cooling vehicle, main coolant temperature sensor andmain coolant temperature control for detecting and maintaining thetemperature of the fluid coolant at a temperature below saidpredetermined temperature, a flow line, a return line, and arecirculating pump for receiving fluid coolant from said source of fluidcoolant and providing fluid coolant to the workstation and producingcooling of the workstation and work medium therein, a workstationtemperature sensor and workstation temperature control for detecting andregulating the temperature of the workstation, a coolant heater in saidflow line responsive to said workstation temperature control for heatingthe coolant being supplied to the workstation to a temperature nearlyequal to said predetermined temperature as to maintain the workstationand work medium at said predetermined temperature, said workstationtemperature control reducing the heating by said heater while asubstantial differential exists between the workstation temperature andsaid predetermined temperature, and said workstation temperature controlincreasing the heating by said heater as said differential decreases andas the workstation temperature nearly achieves said predeterminedtemperature, a flow regulator in said flow line for maintaining thedesired rate of flow of coolant through said flow line, and a bypassvalve for bypassing both said heater and said flow regulator, therebyproviding a flow of unwarmed coolant to the workstation at an increasedrate of flow, said bypass valve being responsive to said workstationtemperature control.
 16. A temperature control as in claim 15 , whereinsaid main coolant temperature control and said workstation temperaturecontrol are a temperature control computer.
 17. A temperature control asin claim 15 , wherein said temperature control controls the temperatureof a plurality of workstations and work media therein.
 18. A temperaturecontrol for adjusting the temperature of a workstation and a work mediumat a workstation to a predetermined temperature, comprising: aworkstation, a source of fluid coolant, a cooling vehicle, main coolanttemperature sensor and main coolant temperature control for detectingand maintaining the temperature of the fluid coolant at a temperaturebelow said predetermined temperature, a flow line, a return line, and arecirculating pump for receiving fluid coolant from said source of fluidcoolant and providing fluid coolant to the workstation and producingcooling of the workstation and work medium therein, a workstationtemperature sensor and workstation temperature control for detecting andregulating the temperature of the workstation, a coolant heater in saidflow line responsive to said workstation temperature control for heatingthe coolant being supplied to the workstation to a temperature nearlyequal to said predetermined temperature as to maintain the workstationand work medium at said predetermined temperature, said workstationtemperature control reducing the heating by said heater while asubstantial differential exists between the workstation temperature andsaid predetermined temperature, and said workstation temperature controlincreasing the heating by said heater as said differential decreases andas the workstation temperature nearly achieves said predeterminedtemperature, a flow regulator in said flow line for maintaining thedesired rate of flow of coolant through said flow line, and a bypassvalve for bypassing both said heater and said flow regulator, therebyproviding a flow of unwarmed coolant to the workstation at an increasedrate of flow, said bypass valve being responsive to said workstationtemperature control.
 19. A temperature control as in claim 18 , whereinsaid workstation comprises a cooling plate for supporting a wafer whosetemperature is to be regulated.
 20. A temperature control as in claim 18, wherein said workstation comprises a cylindrical collar encompassing ashaft to be cooled, said shaft being connected to an electric motor atone end, and said shaft having a chuck at the end of said shaft distalfrom said motor, said chuck supporting a wafer whose temperature is tobe regulated.
 21. A temperature control as in claim 18 , wherein saidworkstation comprises a liquid-to-liquid heat exchanger for regulatingthe temperature of a fluid passing through said heat exchanger.
 22. Atemperature control as in claim 18 , wherein said workstation comprisesa module having an upper compartment, a lower compartment, and a coolingplate separating said upper compartment from said lower compartment,said module regulating the temperature of materials in said uppercompartment and said lower compartment.
 23. A temperature control as inclaim 18 , wherein said main coolant temperature control and saidworkstation temperature control are a temperature control computer. 24.A temperature control as in claim 18 , wherein said temperature controlcontrols the temperature of a plurality of workstations and work mediatherein.
 25. A process for precisely cooling a workstation and a workmedium at a workstation to a predetermined temperature, comprising thesteps of: rapidly lowering the temperature of the workstation by meansof a fluid coolant whose temperature is below the predeterminedtemperature, until the temperature of the workstation approaches thepredetermined temperature, and introducing heat into the coolant flowingto the workstation, thus slowing the rate of cooling, until thepredetermined temperature is achieved.
 26. The process as in claim 25 ,wherein the temperature of a plurality of workstations is controlled.